Final answer:
The question contains a factual error as none of the listed designers are from Maryland or specifically credited with creating the 'American Look' with dirndl skirts, sundresses, and ballet flats. The 'American Look' is a collective style rather than being associated with one particular Maryland designer.
Step-by-step explanation:
The designer from Maryland who is credited with the 'American Look' alongside the dirndl skirt, sundresses, and ballet flats is not Coco Chanel, Christian Dior, Ralph Lauren, or Betsey Johnson, as none of them are from Maryland. The question seems to be a mix-up since the 'American Look' is generally attributed to a number of American designers, but it is not associated with a single designer from Maryland. The 'American Look' was particularly popular in the post-World War II era and was typified by casual yet chic sportswear. However, the designers mentioned are celebrated for their significant contributions to fashion: Coco Chanel is known for her timeless designs and liberating women from the corseted silhouette, Christian Dior for his iconic 'New Look', Ralph Lauren for embodying American style in sportswear, and Betsey Johnson for her whimsical and feminine designs.